Biochem Carbs Lecture 1

Question 1

Sugars, starches, and cellulose are common

These are dietary staples

This is found in the cell walls of plants and has a structural role

Answer 1

Carbohydrates

Sugars and starch

Cellulose

Question 2

What is the general formula for carbohydrates?

Answer 2

Cn(H2O)m where n greater than or equal to 3

Question 3

Name the 2 categories of carbohydrates

Some also contain these 3 elements

Answer 3

Polyhydroxy aldehydes or ketones

Nitrogen phosphorous and sulfur

Question 4

For most simple sugars, m=?

therefore, the empirical formula of simple sugars is

Answer 4

m=n

(CH2O)n

C5H10O5= (CH2O)5
C6H12O6= (CH2O)6

Question 5

These are the simple sugars, with monomer units of more complex carbohydrates

Whats the most abundant one?

Answer 5

Monosaccharides

d-glucose (dextrose)

Question 6

Short chains of monosaccharides joined by _______ bonds, like the disaccharide sucrose (table sugar

Answer 6

Glycosidic

Question 7

Sugar polymers that contain 20+ monosaccharide units, like cellulose

Answer 7

Polysaccharides

Question 8

Sugars that contain an aldehyde group are

Sugars that contain a keto group are

Answer 8

Aldoses

Ketoses

Question 9

3,4,5,6,7 carbon sugars

Answer 9

tritose (?), tetrose, pentose, hexose, heptose

Question 10

Names can be more specific, glucose is an ______ (has an aldehyde carbonyl group and 6 carbons

Answer 10

Aldohexose

Question 11

D or L is assigned to which carbon?

Answer 11

The penultimate carbon, the chiral carbon furtherst from the carbonyl carbon

Question 12

The sugars with the boxes around their names in the handout are the most common in nature. They are all in __ form

Answer 12

D form

Question 13

These are the two most common simple sugars in nature

Answer 13

D-glucose D-fructose

Question 14

D-ribose and 2-deoxy-ribose are components of ___

Answer 14

Nucleic acids

Question 15

Compounds among the D-aldoses and D ketoses corresponding to the same number of atoms are _____ of each other

Answer 15

Diasteriomers (non mirror images)

Question 16

There are ______ stereoisomers where n = number of chiral centers

Answer 16

2^n

Question 17

The aldohexoses have how many carbon centers?

Therefore, how many stereoisomers do they have?

Answer 17

4

16 (2^4)

Question 18

In aqueous solution, aldotetroses and all monosaccharides with 5 or more carbon atoms occur predominately as ___ structures

Answer 18

Cyclic

Question 19

In the formation of the cyclic structures of carbohydrates, the ring structures form as a result of a general reaction between alcohols and aldehydes or ketones to form ___ and ____

Answer 19

Hemiacetal, kemiketal

Question 20

Does hemiacetal/hemiketal formation create a new chiral center?

Answer 20

Yes.

Question 21

With the formation of a new chiral center, two stereoisomeric forms result, what are they?

Answer 21

α and β anomers

Question 22

Six membered ring structures are called _____

Five membered ring structures are called

Answer 22

Pyranoses

Furanoses

Question 23

The α and β anomers of D glucose interconvert in aqueous solution by

Answer 23

Mutarotation

Question 24

A solution of α-D-glucose and β-D-glucose forms an identical equilibrium mixture with identical __ properties

The mixture has about ____ amount of α-D-glucose and _____ of β-D-glucose

Very small amounts of what occur?

Answer 24

Chiral

1/3 α, 2/3 β

Open (linear chain) and five membered ring forms

Question 25

Which is more stable, the α or β anomer of glucose?

Answer 25

β form

Question 26

When switching between D and L forms of a sugar, do all of the chiral carbons have H and OH switch positions in the fischer projections?

Answer 26

Yes! They all do. Not just penultimate carbon

Question 27

Is the pyranose ring planar? What conformation is it?

Answer 27

No. Chair conformation

Question 28

The β anomer should be more stable in the chair conformation because the C-1 OH group is ___

Answer 28

Equatorial (axial in α)

Question 29

In general, substituents in the equatorial positions are less hindered ____ly by neighboring substituents

Answer 29

Sterically

Question 30

Monosaccharides can be oxidized by a relatively mild _____ agent. What is an example of one? The carbonyl group is oxidized to a ___ group

Answer 30

Reducing agent Ex: Cu(2+) carboxyl group

Question 31

Sugars like glucose that reduce metal ions are called ____ sugars

Answer 31

Reducing sugars

Question 32

_____'s reaction measures the amount of oxidizing agent reduced by a sugar. It can be used to estimate the concentration of glucose in the blood and urine (diabetes test) What is currently used as amore sensitive measure for blood glucose levels?

Answer 32

Fehling's Reaction The enzyme glucose oxidase

Question 33

Disaccharides are composed of two ___ covalently linked through a ______ bond

Answer 33

monosaccharides O-glycosidic bond

Question 34

The disaccharide is formed when the ____ OH of one sugared is replaced by the O of an OH group of another sugar What is eliminated? What is formed?

Answer 34

Anomeric OH group Water (condensation reaction) Acetal from a hemiacetal

Question 35

Acetals and ketals of sugars are called ____

Answer 35

Glycosides

Question 36

1. To name disaccharides and oligosaccharides, give the configuration and the ___ C that joins the first monosaccharide unit to the second 2. Name the nonreducing sugar, insert ____ and ___ to distinguish between 5 and 6 membered rings 3. Name the second residue. If there is a third residue, describe the second glycosidic bond by the same conventions

Answer 36

Anomeric Furano, Pyrano

Question 37

_____ is a disaccharide of α-D-glucose and β-D-fructose linked by the O from the anomeric C1 of ____ to the anomeric C2 of ____

Answer 37

Sucrose anomeric C1 of glucose to anomeric C2 of fructose

Question 38

Since both of sucrose's anomeric bonds are involved in glycosidic linkage, sucrose is a ____ sugar, or glycoside Practice naming structure of sucrose in lecture (slide 16)

Answer 38

Nonreducing sugar

Question 39

Maltose is made of two ___ residues The O-glycosidic linkage occurs between the ____ of one glucose and the ____ of the other

Answer 39

D-glucose C1 and C4

Question 40

Maltose retains one free anomeric carbon, so it is a ______ sugar The configuration of the anomeric carbon on the glycosidic link is The glucose residue with the free anomeric carbon can be

Answer 40

Reducing α α or β

Question 41

Maltose is (name it) Using abbreviated nomenclature, it is

Answer 41

α-D-glucopyranosyl-(1→4)-D- glucopyranose Glc(α 1→4)Glc

Question 42

Trehalose is the disaccharide of _____ joined through the ____ anomeric carbons of borth glucose residues

Answer 42

D-glucose C1 anomeric carbons of both

Question 43

Is Trehalose a reducing sugar? Where does it play a major part?

Answer 43

No (no free anomeric C1s The circulating fluids of insects

Question 44

Most carbohydrates in nature are This type is made of a single kind of monomer This type contains two or more different types of monomers Note: you don't have to draw the polysaccharides

Answer 44

Polysaccharides Homopolysaccharide Heteropolysaccharide

Question 45

Polysaccharides used for energy storage are - -> in plants - --> in animals

Answer 45

Starch (in plants) Glycogen (in animals)

Question 46

Polysaccharides used as structural elements are (in plants and animals)

Answer 46

Cellulose (in plants Chitin and Detran (in animals)

Question 47

This homopolysaccharide is amixture of amylose and amylopectin, Amylose and amylopectin are polysaccharides of D-glucose joined by α or β ______ and α or β ______ linkages?

Answer 47

Starch α 1→4 and α1→6 linkages

Question 48

This homopolysaccharide is also a polymer of D-glucose, but it is more extensively branched and more compact than starch

Answer 48

Glycogen

Question 49

This homopolysaccharide is a polysaccharide of D glucose joined by α or β ____ linkages?

Answer 49

β 1→4 linkages

Question 50

Glycogen and starch ingested in the diet are hydrolyzed by ________, They are enzymes in saliva and intestines that break ___ linkages

Answer 50

α-amylases α1→4 linkages

Question 51

In contrast to glycogen and starch, cellulose is not a digestible food source for people because they do not have enzymes to hydrolyze the ____ linkages between glucose units in cellulose

Answer 51

β 1→4